1. Field of the Invention
The present invention relates to a valve unit that can close a channel in a timely manner so as to block fluid flow and can open a channel at a predetermined time so that a fluid can flow along the channel, and an apparatus having the same.
2. Description of the Related Art
Generally, a substrate (i.e., a chip) used for a biochemical reaction such as a lysis reaction or a polymerase chain reaction (PCR) is provided with a micro-channel constituting a flow path. In order to prevent the fluid from being vaporized or flowing during the biochemical reaction, the micro-channel should be closed on time. A micro-valve unit has been proposed to control the flow of fluid in the micro-channel.
One of such micro-valve is shown in FIG. 1. FIG. 1 is a top view of a conventional valve disclosed in U.S. Pat. No. 6,679,279 and Anal. Chem. Vol. 76, pages 1824-1831, 2004.
Referring to FIG. 1, a conventional valve unit 10 includes a channel 12 formed on a substrate 11, an air pump 15 connected to the channel 12, and paraffin wax P provided on a connecting passage 16 between the air pump 15 and the channel 12. In order to heat the air pump 15 and the paraffin wax P, a heating plate 20 is mounted on the substrate 11. The paraffin wax P undergoes solid-liquid-phase transition in response to changes in temperature. In initial stage, the paraffin wax P is in solid and clogs the connecting portion 16. Upon an application of heat generated by the heating plate 20, the paraffin wax P is melted, and the air pump 15 is activated, the melted paraffin wax P′ is pumped toward the channel 12 by the air expansion in the air pump 15, as shown by the double dashed line of FIG. 1. The reference number 13 denotes a main reaction chamber 13 where a biochemical reaction occurs.
However, in the conventional valve unit 10, the air pump 15 and the heating plate 20 are provided on the substrate 11, making it difficult to miniaturize and fabricate the substrate 11. In addition, it takes a relatively long time to close the channel by re-solidifying the paraffin wax that is melted by the heat and directed to the channel. Therefore, it is difficult to precisely control the closing timing of the channel 12.